Coated fabric



Patented Jan. 22, 1946 COATED FABRIC Camille Dreyfus, New York, N. Y.

No Drawing. Application August 5, 1942,

Serial No. 458,718

4 Claims.

This invention relates to coating compositions, and relates more particularly to coating compositions for coating textile fabrics which are employed in covering airplane surfaces.

An object of my invention is the application of a smooth, impervious base coating having a basis of cellulose acetate. or other organic ester of cellulose, of relatively low degree of esteriflcation to a textile fabric employed for covering airplane wing, fuselage and control surfaces.

Another object of my invention is to apply a base coating to said textile fabrics which clings tenaciously to the fabrics and which renders the same more receptive to the application of further coating compositions.

Other objects of my invention will appear from the following detailed description.

In the construction of many types of airplanes wherein the wing load is light, cloth is employed extensively for covering wing, fuselage, tail and other surfaces of the airplane. To be satisfactory, such cloth must possess great strength. Generally, such cloth is woven in a tight compact weave from yarns of high tenacity'so as to form a fabric capable of resisting the various stresses and strains placed upon it. In order to weather-proof the fabrics and also to cause them to fit tightly and smoothly over the frame or structure of the airplane after they are attached thereto, the fabrics are usually coated with coating compositions having a basis of a derivative of cellulose which formv a smooth, impervious, weather-proof film thereon. The effect of the coating composition is two-fold. Not only does it form the necessary smooth weather-proof film, but it likewise shrinks on drying and causes the'fabric to which it is applied to become taut and to ilt tightly on the airplane frame, thus presenting a surface of the proper aerodynamic characteristics.

It has been frequently observed, however, that the coating compositions do not adhere with a satisfactory degree of permanence to the surface of said fabrics. Even after relatively short periods of service the coating often separates from the fabric and forms blisters which crack and cause the coating to peel off, thus exposing the fabric to the destructive action of the elements.

I have now discovered that weather-proof coating compositions may be caused to adhere tenaciously to airplane fabrics by employing, prior to the application of said weather-proof coating composition to the fabric, a base coating having a basis of cellulose acetate, or other organic ester of cellulose, of relatively low degree of esterification. The novel base coating of my invention not only aids in causing the fabric to be stretched tautly across the airplane structure but exhibits an unusual degree of adherence to the fabric as well. When weather-proof cellulose derivative coatings are applied over the base coating, the former becomes strongly attached to said base coating and the weather-proof film formed over the base coating is thereby strongly bonded to the fabric. The weather-proof film obtained, after employing the novel base coating composition of my invention, adheres to the fabric with increased strength and tenacity and the coated fabric remains free of blister, peeling and cracking even after long and hard service.

While any organic ester of cellulose of relatively low degree of esteriflcation may be employed in forming the base coating in accordance with my invention, such as, for example, cellulose propionate, cellulose butyrate and mixed esters such as cellulose acetate-propionate and cellulose acetate-butyrate of a relatively low degree of esteriflcation, .my invention willbe more particularly described in connection with the use of low acetyl cellulose acetate, and especially cellulose acetate having an acetyl value of to calculated as acetic acid.

The low acetyl cellulose acetate may be prepared by esterifying cellulose with an esterifying agent such as acetic anhydride or other organic acid anhydride in the presence of a catalyst, for example, sulfuric acid, and a diluent such as acetic acid. The cellulose. acetate may then be ripened or hydrolyzed to the low acetyl value in the manner well known in the art. The cellulose acetate may be ripened directly or ripening may be interrupted at some convenient point, the'cellulose acetate precipitated and, after washing and stabilizing, the ripening may then be continued in the presence of the same or a different ripening agent. The most desirable results are obtained, however, if the low acetyl cellulose acetate, or other cellulose ester employed, is ripened or hydrolyzed to the low acetyl value in a plurality 40 of stages in the manner more particularly described and claimed in United States Patent No. 2,329,706.

The novel base coating composition employed in accordance with my invention comprises low acetyl cellulose acetate dissolved in a suitable volatile solvent, or mixture of solvents, in which.

solution may be incorporatedone or more plasticizers to increase the flexibility of the base coating upon evaporation of the solvent. To improve the strength of the film, natural or synthetic resins may also be included in the base coating composition.

Any suitable volatile solvent for the low acetyl cellulose acetate may be employed such as, for example. ethyl alcohol, acetone, butyl alcohol, ethyl acetate, butyl acetate, butyl propionate, ethyl lactate, diacetone alcohol and ethylene dichloride. In order to modify the drying and other characteristics of the coating compositions such as the flow characteristics, for example, non-solvents for the low acetyl cellulose acetate such as benzol, toluol, xylol, solvent naphtha and benzine may be added to the coating composition.

Suitable plasticizers which may be employed to impart the desired flexibility to the base coating include the dimethyl ether of ethylene glycol phthalate, dimethyl phthalate, ethyl phthalyl ethyl glycollate, triethylene glycol, triacetin. tripropionin, mono-ethyl-p-toluene sulfonamide, triphenyl phosphate, tricresyl phosphate, diethyl phthalate. dimethoxy ethyl phthalate, dibutyl tartrate, camphor and dibutyl phthalate.

Among suitable synthetic resins which may be incorporated in the base coating composition are 1 those obtainable by the condensation of phenols with aldehydes or ketones, those obtainable by the condensation of urea with aldehydes, such as formaldehyde, the condensation products of phthalic anhydride, or .other dibasic acid anhydrides, with polyhydric alcohols such as glycerol, and many others. Natural resins such as kauri, copal, manila copal, and congo copal, and gums such as gum elemi are also suitable.

In forming the base coating composition, the low acetyl cellulose acetate may comprise from 8 to 30% by weight of the composition, the solvent from '70 to 90% by weight, and the plasti cizers 2 to 5%. When resins or gums are employed, they may comprise 0.5 to by weight of the composition.

The top coating applied over the base coating composition to increase the weather-proof and/or weather resistant properties of the coated fabric may have, as the main film-forming constituent thereof, any suitable cellulose derivative. For example. organic esters of cellulose of a higher degree of esterification than those employed for the base coating are suitable. Cellulose acetate of an acetyl value of from, say, 53 to 56% may be employed, as well as other organic esters of cellulose of equivalent degree of esterification. Cellulose ethers such as ethyl cellulose and benzyl cellulose, and inorganic esters of cellulose such as cellulose nitrate likewise yield top coating compositions of excellent characteristics. In forming the top coating compositions. volatile solvents or mixtures of solvents such as those mentioned above, as well as those natural and/or synthetic resins and plasticizers employed in formulating the base coating are suitable. Coating compositions containin rubber and rubber derivatives such as rubber hydrochloride or chlorinated rubber, may also be employed over the top coating to improve the weather-resistant properties of the coated fabric.

In order further to illustrate my invention but without being limited thereto, the following example is given:

Example Acetone 395 Methyl ethyl ketone 67 Ethyl alcohol 92 Benzol 102.5 Benzyl alcohol 17.5 Triphenyl phosphate 15.0

After the coating has dried to a strong adherent ilim which causes the fabric to shrink somewhat, the fabric is then coated with one or more coats of the following top coating composition:

Partsby weight Cellulose acetate (54.5% acetyl, calculated as acetic acid 150 Glyceryl phthalate Ethylene dichloride 750 Ethyl alcoh 183 Methyl glycol 96 Methylglycol acetate 100 As the coating composition dries, the fabric shrinks and is caused to fit tightly over the airplane structure. The top coating forms a smooth, impervious, weather-proof film. Due to the presence of the low acetyl cellulose acetate base coating, the film formed on application of the top coating adheres very strongly to the fabric. The smooth, adherent film remains free of blisters and is unusually resistant to any cracking and peeling even after long and severe service.

It is to be understood that the foregoing detailed description is given merely by way of iilustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

1. Process for the preparation of a fabric having a strongly adherent coating thereon, which comprises applying a liquid base coating composition having a basis of an organic acid ester of cellulose of relatively low degree of esteriflcation having an acyl value equivalent to that of cellulose acetate having an acetyl value of about 40 to 45% calculated as acetic acid to said fabric, allowing said coating composition to dry, and covering the base coating thus formed with a coating composition comprising an organic acid ester of cellulose of a higher degree of esteriflcation having an acyl value equivalent to that of cellulose acetate having an acetyl value of about 53 to 58% calculated as acetic acid.

2. Process for the preparation of a fabric having a strongly adherent coating thereon, which comprises applying a liquid base coating composition having a basis of cellulose acetate of an acetyl value of 40 to 45%,calculated as acetic acid, to said fabric, allowing said coating composition to dry, and covering the base coating thus formed with a coating composition comprising cellulose acetate of an acetyl value of 53 to 56%, calculated as acetic acid.

3. A coated fabric having a strongly adherent coatingthereon, said coating comprising a base coating having a basis of an organic acid ester of cellulose of relatively low degree of esteriflcation having an acyl value equivalent to that of cellulose acetate having an acetyl value of about 40 to 45% calculated as acetic acid upon which is superimposed a coating comprising an organic acid ester of cellulose of a higher degree of esteriiication having an acyl value equivalent to that of cellulose acetate having an acetyl value of about 53 to 56% calculated as acetic acid.

4. A coated fabric having a strongly adherent coating thereon, said coating comprising a base coating having a basis of cellulose acetate of an acetyl value of 40 to 45%, calculated as acetic acid, upon which is superimposed a coating comprising cellulose acetate of an acetyl value of 53 to 56%, calculated as acetic acid.

CAMILLE DREYFUS. 

